1. Field of the Invention
The present invention relates to a parking-brake operating device for selectively placing a parking brake of an automotive vehicle in its operative and inoperative positions, and particularly to improvements of such devices which are adapted to prevent the parking brake from being erroneously released from its operative position to its inoperative position, for example upon erroneus operation or pushing of the associated knob.
2. Priort Art Statement
A variety of parking-brake operating devices have been used for selectively placing an automobile's parking brake in its operative and inoperative positions. The Japanese Utility Model Laid-Open Publication No. 56-119760 discloses one example of such parking-brake operating devices, which includes (a) an operating lever which is selectively placed in its first and second positions to place the parking brake in its operative and inoperative positoins, respectively, the lever being disposed pivotably about a first pivot axis and connected to the parking brake through a brake cable, the lever including a free-end portion having a free end, the portion having a longitudinal hole which is formed therein longitudinally of the lever and is open in the free end; (b) a stationary sector having a plurality of teeth; (c) a pawl supported by the lever pivotably about a second pivot axis parallel to the first pivot axis, the pawl having a first and a second arm; (d) a knob having a first and a second end, and fitted, over an axial part thereof having the first end, in the longitudinal hole of the lever such that the knob is retractable inward upon operation thereof on the second end, the axial part having an axial recess which is formed therein and is open in the first end and a lateral surface adjacent to the first end, the knob having at its first end a stopper protruding radially inward from an inner wall surface thereof defining the axial recess; (e) a release rod having a first and a second end, the second arm of the pawl being connected to the first end, the rod including a head having the second end, the head being fitted in the axial recess of the knob such that the head is engageable with the stopper; (f) a first spring possessing a first biasing force for permitting the pawl to be pivoted about the second pivot axis in a first direction in which to cause the first arm of the pawl to be engaged with the teeth of the sector; and (g) a second spring fitted in the axial recess of the knob and possessing a second biasing force for permitting the head of the rod to be engaged with the stopper of the knob, the second biasing force being determined such that, upon retraction of the knob when the lever is held in its second position, the second spring causes the rod to be moved relative to the lever with the head engaged with the stopper, whereby the pawl is pivoted in a second direction opposite to the first direction and released from the engagement with the sector, and that, upon retraction of the knob when the lever is held in its first position, the second spring permits the knob to be moved relative to the rod, while the second biasing force is overcome by pivot resistance associated with the forced engagement between the pawl and the sector due to a tension force of the brake cable, whereby the rod is not moved relative to the lever and the pawl is not released from the forced engagement with the sector.
This parking-brake operating device is adapted to prevent the parking brake from being erroneously released from its operative position to its inoperative position, for example when the knob is erroneously operated or pushed inward in the longitudinal hole of the operating lever. In such cases, the second spring is deformed, permitting the knob to be moved relative to the release rod. Thus, the parking brake of the prior-art operating device does provide an operator with a degree of safety. Further, since the second spring and the head of the release rod are received in the axial recess of the knob through the opening of the axial recess in the lateral surface of the knob, the operating device is easily fabricated within a short time. The parking brake of the prior art is released from its operative position to its inoperative position by pivoting the lever about the first pivot axis, specifically by slightly raising the lever, and that releases the pawl from the forced engagement with the sector due to the tension force of the brake cable and subsequently pushes the knob inward in the longitudinal hole of the lever.